Process of making articles by electroplating.



PATENTED SEPT. 8, 19 08.

T. A. EDISON. PROCESS OF MAKING ARTICLES BY ELEGTROPLATING.

APPLICATION FILED NOV. 3, 1906.

2 SHEETS-SHEET 1;

. UNITED STATES;

THOMAS A. EnIsdii,

NEW JERSEY.

or LLEWELLYN PAR1 ,,OItllNGE, "NEW JERSEY,- AssIGiIoR TO EDISON 3 SP MA winsa anecrziei iiaen agr I Specification of Letters Patent.

" Patentedfs e'pt. 8, 1909.-

Original application filed Octobor'li, 1908, smart. 176,818, Divi dcd this application filed November 8, 1906.

Serial No. 341,861. 1

To all whom it may concern." i? Be it known that I, THOMAS A. EDISON, of Llewellyn Park, Orange in the county of Essex and State of New jersey, have invented certain Improvements in the Process of Makin Articles by Electroplating, of which the following is a description.

This application is a division of Patent No. 850,912; granted April 23', 1907. My invention relates to an improved process for makin' articles by electro-plating,

and, particular y, for makin r cans or receptacles for use with storage batteries of my improved type, and as I describe in Patent No. 857,041, granted June 18, 1907. The process has been gotten up especially with the object in min of making such cans or receptacles of iron, but it may be carried out for the manufacture of other articles and from other metals or combinations thereof.-

The particular value of a can or receptacle for stora e batteries made by a plating process, as I s all describe, resides in the fact that such an article is entirely seamless, so that the necessity is done away with of employing solder, which may be affected by the alkaline electrolyte used with such batteries. The problem of making a storage battery can or receptacle, or other essentia ly hollow article, by a plating process of iron, presented very great practical difficulties, since such metal during a plating olperation tends to contract,- and, unless specia provision is made to overcome the same, the contraction will result in the metal cracking or scalin from any molds or forms on which it maye plated. Furthermore, in the plating of iron, the formation of gas bubbles would result in the deosited coating being pitted or actually perorated, which would of course destroy the utility of the completed artic e. Furthermore, an electro-deposited coating -of iron is extremely weak'and brittle in nature, and articles made therefrom without subsequent treatment would noth'e available for com- I mercial use. The process whichI have-invented and which will beipresentl'y described hasbeen evolved after a long series of explated article, such as a batte can or'rece tacle, which may be madeo iron, which w'l be perfectly smooth and coherent throughout, being entirely free of pits or holes, and which, when finished, is very strong and tough.

order thattheinvention may be better un erstood, attention is directed to the accompanying drawings forming a part of this specification, and in which:

Figure 1, is across-sectional view, taken through one of the plating tanks which is used in carrying my process into effect, the assumption being made that the articles which are to be produced are one piece battery cans or receptacles; Fig. 2, a separate side elevation of the mold or former used in the manufacture of such cans or rece tacles Fig. 3, a cross-sectional view on t e lines 3-3 of Fig. 2, looking downwards; and Fig.- 4, a view corresponding to Fig. 3, showing a modification.

In all of the above views corresponding parts are,represented by the same numerals of reference. 1.

In the carrying of my process into effect and in the preferred embodiment thereof, I make use of three plating tanks in which distinct plating operations take place. I prefer to use three separate tanks in order that the operations may be continuous, so that while one plating is goin on in one tank a succeeding plating may be ta ing place in another tank,

and so on. It will, however, be understood that the same tank may be used for the several platings, although in that case it will obviously have to be cleaned out and a fresh solution used for the subsequent plating o erations. The several tanks used may be a of the same construction, so that a descri tion of one will sufiice for all.

e tank 1, is in the form of a long, open trough, having one or more wooden crossieces corresponding to the several molds or fbrmers which may be used therein. Each cross-piece 2, is formed with a bearing 3, in which is mounted bevel-gear 5, at itsupper end. Meshing with each of the gears 5', 1s a bevel-gear 6, on a longitudinal shaft 7. In thisway it will be obvious that a plurality of the shafts 4, ma

be driven from the same main shaft. Eac periments, and results in the production of a of the molds 8, is made of the roper form or shape, being composed prefera ly of brass or copper, and being hollow'so as to be as light as possible. Each mold is provided with a bridge piece 9, at its upper end, with which a vertical shaft 4, having a the lower threaded end of the shaft 4, en-

gages, so-that the mold will be rotated by said shaft. Each of the molds is provided with a removable section 10, which may be separated from the main ortion of the mold to facilitate the remova of the completed article, as will be explained. The removable section 10, of each mold may be normally held in position in any suitable way, as, for example, by means. of-a hook 11, engaging over a bridge-piece 12, (as shown in Figs. 2 and 3), or by a dove-tailed joint 13, between the two sections, (as shown in Fig. 4). The mold 8, constitutes thecathode of the plating bath, suitable anodes 14, being arranged therein, and being connected with a suitable source of supply 15, either a battery or plating dynamo. The mold 8, is preferably slightly tapered towards its lower end to facilitate the removal of the completed article. This taper may be very slight indeed, and need not be more than one-sixteenth of an inch.

. Assuming three plating baths to be em ployed and the preferred process to be carried out in connection with the manufacture of battery cans or rece tacles of iron, I proceed substantially as ollows: The mold is first dipped in melted paraffin wax maintained at a temperature of about one hundred degrees centigrade, so as to coat the mold with a very thin layer thereof. layer need not be more than .005 to .025 inch in thickness. After the wax layer has cooled and congealed I apply thereto a conducting material in finely divided form, preferably graphite, so as-to entirely coat the mold, the

- coating of wax being so thin that the graphite apparently makes contact through the same with the mold. I preferto make use of a preliminary coating of wax, as ex lained,

-- since this not only facilitates the a p ication of the gra hits, but also permits t e article, when finis ed, to be readily removed. The coated mold is now placed in a copper bath with copper anodes, and is copper-plated to a thickness of about .004inch, more "or less. The solution used may be the ordinary copper sulfate (CuSOQ solution- After the l'ating of copper has .been applied the mo d is removed and washed and ntroduced into a second tank having a nickel plating solution therein. An suitable so ution may be employed, suc as a nickel-ammoniumsulfate solution. In this bath the mold is plated with an extremely thin coating of nickel, about .001 inch in thickness. The mold is then removed-and washed and put into the third tank employing iron,electrodes, and having a solution consisting preferably of ferrous-ammonium sulfate Fe (H N) (SO It is important that this iron solution' should be absolutely n utral and free from ferric salts, since the presence of any traces of acidity, or of ferric This bility of the bathbecoming acid may be prevented, I preferably add small quantities of ammonia or other alkali thereto at suitable intervals. The plating of iron is effected preferably by a current of about 1 to 1.2

amperes per square decimeter of surface.

The plating of iron is continuedfor from thirty to thirty-five hours at a tem erature of not below forty degrees centigra e, thereby giving a coating about .020 inch in thickness.

If the bath is materially cooler'than this, say

at the ordinary temperatures, I have found from my experiments that the deposit tends to crack after a few hours. It will, of course,

be understood that when heavier or lighterlayers of iron require to be deposited, the time during which the coating takes place will be proportionately increased or diminished.

In order to prevent the formation of pits or holes in the deposited iron coating, which would be likely to form by the accumulation of gas bubbles thereon, and to secure a very smooth surface, I introduce a quantity. of crushed charcoal into the solution, whereby the added material will rub over and scour the surface of the d?osited metal to polish.

the same and wipe 0 any gas bubbles which may-tend to accumulate thereon. Furthermore, I find that a small percenta e of carbon will in this way be incorporate with the deposited iron, which, therefore, in the subsequent annealing, is converted practically into a superior product of soft steel, containing, according to my analysis, almost 4% of carbon. As a result the finished article is considerably tougher and more than when made of-pure iron. Such particles of charcoal may vary in dimension between one-sixteenth to one-ei hth of an inch in size. Of .course, it may e possible that other materials may be used for this purpose, but I have found that charcoal is very desirable for this use. The amount tion may obviously vary within quite wide 'of charcoal which is thus added to the solulimits, but good results are secured when the bulk of charcoal introduced is about one half the bulk of thesolution, sothat if the charcoal is allowed to float it will form a layer extending about half the thickness of the solution in the tank. During the 11'011 plating the mold is revolved. at a speed of about ninety turns per minute, but this speed is also variable and need not be strictly adhered to. v

After a plating of iron of-the desired thickness has been formed on the.mold,thelatter is removed from the tank, and washed in water at a temperature of about seventyfive degrees centigrade, thereby melting the wax originally deposited on the mold, after which, by removing the removable section of the mold, the resulting casing or can or other article can be se arated therefrom, as will be understood. ron which has been thus plated on a mold is extremely brittle, and, in order that it may be made tough and strong, I prefer to anneal the same. For

this purpose the articles, after plating, are' introduced into a closed retort and heated to a red heat, being then allowed to slowly cool. Preferably this heating of the articles is effected in a non-oxidizing atmosphere, such as in an atmosphere of hydrogen gas, so as to remove any possibility of oxidizing, and, after annealing, the articles are allowed to cool in the same atmosphere. In the case of storage battery cans or'receptacles, it is necessary that the co per originally de osited on the graphite sl fould be remover since this metal is slightly soluble in an alkaline electrolyte in the presence of electrolysis.

.This removal of the original copper coating is preferably effected by filling the can or receptacle with a solution of a mixture of copper nitrate Cu(NO and sodium nitrate.

(NaNO or sodium nitrate can alone be used in the solution. The can or receptacle is now used as an anode of a plating bath, a cop er cathode being'introduced therein and a p ating current applied. When the solut1on contains copper nitrate, as is preferable,

the copper will be plated off from the inside of the can or receptacle and be recovered on the cathode; but when sodium nitrate is alone used the copper thus removed forms insoluble copper hydrate, which can be recovered from the solution in any suitable way. I prefer to apply a preliminary coating of copper, since I find that the iron tends to crack after a few hours plating, owing to its tendency to constantly contract, and the copper appears to offer a base or foundation on which the iron is deposited and which resists the tendency to contraction. The de osit of nickel is applied to the copper in or er that the final article may be provided with a nickel interior.

This is of importance in connection with cans or rece tacles for storage batteries, in order that the iron may be protected from the efiects of any erratic electrolytic action in the alkaline solution.

After the cop er coating has been removed, as explained, t e article is trimmed on its upper edge ready to receive the cover or cap, and, if desired, its sides ma be provided with horizontal corrugations l ocated Within the edges of the can so as to stiffen the same, as I describe in my Patent No. 852,424, granted May 7, 1907. Finally, the can or receptacle is nickel-plated on its outside so as to protect the same from oxidation, and, if desired, an additional coating of nickel may be applied to the inside thereof and welded thereto. The can or receptacle is now finished, and is ready to receive the electrodes, after which the top or cover is soldered in place. Cans made inthis way can be manufactured very cheaply, they are of and tough, t ey are free from pits or holes, they do away entirely with the necessity of using superior ap earance, they are very strong Having now described my invention, what I claim as new therein'and desire to secure by Letters Patent is as follows:

1. The process of making a storage battery can or receptacle, which. consists in electroplating .a coating of copper on a former, in

eleotro-plating a film of nickel on the copper coating, and in electro-plating a film of iron on the nickel film, whereby a seamless article will be produced, substantially as set forth.

2. The process of making a storage battery can or receptacle, which consists in electroplating copper on a former, in electro-plating a film of nickel on the copper-coating, 1n electro-plating a film of iron on the nickel coating, and in finally removing the copper deposit, whereby a seamless can or receptacle having a nickel-plated interior wih be formed, substantially as set forth.

This specification signed and witnessed this 2nd day of November, 1906.

THOMAS A. EDISON.

Witnesses: I FRANK L. DYER, ANNA' R. KLEHM. 

